Subject code :(17651) 1 25msbte.engg-info.website/sites/default/files/summer 201… · ·...

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)

(ISO/IEC - 27001 - 2005 Certified)

SUMMER-16 EXAMINATION Model Answer

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Subject code :(17651) Page 1 of 25

Important Instructions to examiners:

1) The answers should be examined by key words and not as word-to-word as given in the model answer scheme. 2) The model answer and the answer written by candidate may vary but the examiner may try to assess the understanding level of the candidate. 3) The language errors such as grammatical, spelling errors should not be given more Importance (Not applicable for subject English and Communication Skills. 4) While assessing figures, examiner may give credit for principal components indicated in the

figure. The figures drawn by candidate and model answer may vary. The examiner may give credit for any equivalent figure drawn.

5) Credits may be given step wise for numerical problems. In some cases, the assumed constant values may vary and there may be some difference in the candidate’s answers and model answer. 6) In case of some questions credit may be given by judgement on part of examiner of relevant answer based on candidate’s understanding. 7) For programming language papers, credit may be given to any other program based on

equivalent concept.




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Q No. Answer marks Total

marks

1 Attempt any FIVE of the following 20

1a Six major refineries in India.

1. Reliance petroleum Ltd, Jamnagar.

2. Indian Oil Corporation Limited, Koyali in Gujarat.

3. Manglore Refinery and Petrochemicals Ltd, Manglore in Karnataka.

4. Chennai Petroleum Corporation Ltd, Manali

5. Cochin Refineries Ltd, Cochin , Kerala.

6. Hindustan Petroleum Corporation Ltd, Visakhapattanam in Andhra Pradesh.

7. Indian Oil Corporation Limited, Panipat in Haryana.

8. Hindustan Petroleum Corporation Ltd, Mumbai

9. Bharat Petroleum Corporation Ltd, Mumbai.

10. Indian Oil Corporation Limited, Mathura in Uttar Pradesh.

Largest refinery: Reliance petroleum Ltd, Jamnagar.

1/2 mark

for any six

1

4

1-b OPEC

OPEC is Organization of Petroleum Exporting Countries. . 43% of world crude

produced is shared among the group members. OPEC is a 13 member body

consisting of Algeria, Iran, Iraq, Saudi Arabia, Gabon, Kuwait, Ecquador,

Libya, Indonesia, Nigeria, Qatar, UAE and Venezuela.

Names of four oil producing countries in the world.

Russia - 14%

Saudi Arabia - 13%

United States - 9%

China - 5%

2

1/2 mark

for any

four

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Iran - 4.14%

Canada – 4%

1-c Desalting of crude:

Desalting of crude is the removal of corrosive salts and water from the crude

which will otherwise cause corrosion, plugging &catalyst poisoning.

Desalting of crude is done in two ways – 1. By chemical treatment

2. Electric desalting

Electric desalting: The feedstock crude is heated between 1500& 3500F to

reduce viscosity & surface tension for easier mixing & separation of the water.

The principle of operation is that under a charged electric field, the polar

molecules orient. A potential of 20,000-30,000 volts is applied between

electrodes through which crude is passed. Water present in the form of

emulsion also coalesces and agglomerates into a stream entrapping all the salts

in the process. Brine collects at the bottom of the desalter, while crude floats

above and forms a separate stream.

( Description of chemical treatment should also be given due consideration)

4 4

1-d Fractions obtained from crude oil with their boiling point range

Fractions Boiling point range

1. Uncondensed gases <30oC

4

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2. Petroleum ether 30-70oC

3.Gasoline or petrol or motor spirit

40-120oC

4. Naphtha 120-180oC

5. Kerosene oil 180-250oC

6. Diesel oil 250-320oC

7.Heavy oil On vacuum distillation of heavy oil gives lubricating oil, petroleum jelly, greases, paraffin wax etc.

320-400oC

8.Residue > 400oC

1-e Flow sheet for the manufacture of ethylene oxide

4




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4

1-f Denatured alcohol:It is ethanol that has additives in it to make it poisonous to

discourage recreational consumption and at the same time can be used for

diversified industrial applications.

Denaturants :(Any two)

Methanol,isopropyl alcohol, methyl ethyl ketone, methyl isobutyl ketone.

2

1 mark

each

4

1-g Reason for crude oil being called black gold:

Crude oil is yellowish black oil that is extracted from under the surface of the

earth. Itis one of the most necessitated worldwide required commodities. Any

fluctuation in thecrude oil prices can have direct and indirect influence on the

economy of the counties.

4 4

2 Attempt any FOUR of the following 16

2-a Alkylation process:

Sulphuric acid alkylation process:

Reaction:

C4 H8+ C4H10 → C8H18(2,2,4 Trimethyl Pentane)

1

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CH2=CH-CH2-CH3 + CH3-CHCH3-CH3→ (CH3)3-C- CH2-CH-(CH3)2

Feed stock ( propene, butene, isobutane ) enters a multistage cascade reactor.

Iso butane and acid passes from one stage to another cascading serially. Olefin

is split and introduced in to each cascade. To avoid polymerization, large

excess of iso butane is used. Sulphuric acid catalyst is introduced at 4-100C.

alkylate formed is taken out from the reactor, cooled and fractionated.

Isobutane from the fractionator is recycled.

(Hydrofluoric acid alkylation should also be given due consideration)

3

2-b Characteristics of waste water produced in petrochemical plant:

Free oil: 2000-3000 mg/ l

H2S and sulphides: 10-220 mg / l

Phenol : 12-30 mg / l

Suspended solids: 200-400 mg / l

5 day BOD at 200c : 100-300 mg / l

Alkalinity: 10-250 mg / l

4 4

2-c Names of two types of cracking process

Two different types of cracking are thermal cracking and catalytic cracking.

2

4




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Basic difference between thermal cracking and catalytic cracking:

Thermal cracking is a refining process in which heat ( > 800oC ) and

pressure 700KPa) are used to break down, rearrange hydrocarbon molecules.

Catalytic cracking breaks complex hydrocarbon molecules in to simpler

molecules under less severe operating conditions with the help of a catalyst.

2

2-d LEL:Lower Explosive Limit (LEL) is the minimum concentration of a

particular combustible gas or vapor necessary to support its combustion in air.

Below this level, the mixture is too lean to burn.

HEL: The maximum concentration of a gas or vapor that will burn in air is

defined as Higher explosive Limit(HEL). Above this, the mixture is too rich to

burn.

Ignition temperature: The lowest temperature at which a material can catch

fire and burn continuously withoutthe aid of external firing agencies.

1.5

1.5

1

4

2-e Chemicals derived from C1 hydrocarbon (any two)

Methanol, formaldehyde, chloromethane, methylene dichloride.

Chemicals derived from C2 hydrocarbon (any two)

Ethanol, ethylene oxide, styrene, acetaldehyde.

2

2

4

2-f Polymerization:

Poymerisation is defined in petroleum industry as the combining of two or

more olefin molecules to yield larger molecules.

Different methods of polymerization :

The different methods of polymerization are condensation or step growth

polymerization and addition or chain growth polymerization.

Addition polymerization can be further classified into homogeneous and

heterogeneous polymerization.

Homogeneous polymerizations are of two types- bulk polymerization and

2

2

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solution polymerization.

Heterogeneous polymerization are of two types – emulsion and suspension

polymerization.


3-a i) Flash point-It is the lowest temperature at which the oil gives off enough

vapors which ignite for moment, when small flame is brought to near it.

(ii) Drop point-It is the temperature at which the grease passes from a

semisolid to a liquid state under the conditions of test.

(iii) Pour point-The temperature at which oil stops flowing or getting poured is

called pour point of oil.

(iv) Cloud point-When oil is cooled slowly, the temperature at which it

becomes cloudy is called as cloud point.

1 mark

each

4

3-b Manufacture of butadiene:

Description:

A refinery gas of C4/C5 containing n-butane with some isopentane is mixed

with recycle gas & preheated to reaction temp.prior to contact with catalyst in a

fixed bed, regenerative heating reactor system. The temp. of reaction at start of

make period is 6500C,dropping to 5500C at the end before switching to

regeneration. The pressure is low 120-150mm absolute ,to force reaction to

right.

The product gases are oil quenched, compressed,cooled& separated from the

light ends by absorption in naphtha followed by stripping. The overhead is

fractionated to yield crude butadiene at the top which is purified by absorption

using cuprous ammonium acetate,extractive distillation with furfural or

azeotropic distillation with ammonia.

Main reaction-C4H10→CH2=CH.CH=CH2+2H2

Side reaction-C4H10→C4H8+H2

2

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Flow sheet

2

3-c Flow sheet for the manufacture of formaldehyde:

4

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3-d Factors affecting the prices of crude oil 1. Production of crude oil: OPEC nations are the major producers of worlds

crude oil. Any decision by them to increase or decrease production affects the

prices of crude oil.

2. Natural causes (weather) : Extreme weather conditions(hurricanes,

thunderstorms) affects production and increases the prices of oil.

3. Supply and demand: Since OPEC has sufficient reserves, they can directly

influence market pricing especially when supply of oil produced by non OPEC

nation decreases.

4. Restrictive legislation: Energy policies and taxes of oil rich countries

affecttheprices of oil.

5. Political unrest: If an oil rich area becomes politically unstable, supplier

markets react by bidding up the prices of the oil so that supplies are available to

the highest bidder.

6. Production: Location of reserves, amount and properties of oil found ,

geological formation in which oil is found, cost of extraction etc affects the

cost of oil supplied from a particular reserve.

7. Exchange value of dollar: Dollar depreciation tends to increase oil demand

and increases the prices of oil.

1 mark each for

any 4 points

4




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3-e Importance of distillation in oil refining operation:

The crude oil distillation unit (CDU) is the first processing unit in virtually all

petroleum refineries. The CDU distills the incoming crude oil into various

fractions of different boiling ranges, each of which are then processed further in

the other refinery processing units. Crude oil contains various constituents such

as diesel, petrol, asphalt, waxes etc.So for efficient separation of all

hydrocarbons distillation is very important.

4 4

3-f Two Chemicals derived from C3 hydrocarbon with their uses

Acetaldehyde, acetone, glycerin

Acetaldehyde-used in manufacture of acetic acid, acetic anhydride

Acetone-used as solvent,manufacture of bisphenol

Glycerin: used for making alkyl resins, plastics, explosives, food and

pharmaceuticals

Two Chemicals derived from C4hydrocarbon with their uses

MTBE,Butadiene, butanol

MTBE-It is a gasoline additive used to increase octane no. that is produced

from methanol & isobutylene, used as a fuel component in fuel for gasoline

engines.

Butadiene-used in wide variety of synthetic rubbers & polymer resins.

Butanol : used as a blended additive to diesel fuel, solvent for textile and

chemical processes.

1/2 mark each for any two




4

4 Attempt any FOUR of the following

4-a Separation of crude oil by fractional distillation:

The steps of fractional distillation

1. Heating of mixture is done.

2. The mixture boils, forming vapours.

3. The vapour enters to the bottom of the fractional distillation column that is

2

4




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fitted with trays.

4. The vapour rises in the column.

5. The trays have bubble caps in them to allow the vapour to pass through.

6. The trays increases contact time between the vapour& liquid.

7. The vapour rises in the column. As the vapour rises in the column, it

becomes cool.

8. So the trays collect various liquid fractions & the vapours are condensed.

9. In this way crude oil is separated by fractional distillation.

2

4-b Flow diagram for the manufacture of MTBE

4




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4

4-c Udex process for recovery of BTX from reformate gasoline:

Reformate as a feed can be send to the extraction column where reformate is

heated to about 140-1500c in presence of lean solvent. During extraction we get

two phases extract phase &raffinate phase. Extract phase contains aromatic

compounds &raffinate phase contains non aromatic compounds. Solvent is used

to extract aromatic compounds from reformate feed & then it send to the

stripper .In stripping column ,recovery of solvent takes place which is removed

from bottom side ,aromatic extract can be exist from top side. Aromatic extract

phase is cooled & then sentto settler. Two settlers can be used, part of one

settler is feed back again to extraction column as a reflux .Now the remaining

part of aromatic extract phase is fed to wash tower, for washing with water.

Higher % of conc. aromatic extract component can be withdrawn from top as a

product, where water with impurity can be obtained from bottom side.

4

4




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4-d Working of vacuum distillation unit:

Heavier fractions from atmospheric distillation unit that cannot be distilled

without cracking under its pressure & temp. Conditions are vacuum distilled.

Vacuum distillation is simply distillation of petroleum fractions at very low

pressure to increase volatilization & separation. In most system vacuum inside

the fractionators is maintained with steam ejector & vacuum pumps, barometric

condensers or surface condensers. The injection of superheated steam at the

base of vacuum fractionators further reduces the partial pressure of

hydrocarbons in the tower, facilitating vaporization & separation.

2

2

4




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4-e Steps in waste water treatment in petrochemical industry.

Primary treatment -this treatment is the separation of oil, water, hydrocarbon

solids from waste water in two stages .During the first stage, an API separator,

a corrugated plate interceptor, or other separator design is used.Wastewater

moves very slowly through separator allowing the free oil to float to the surface

& be skimmed off &solids to settle to the bottom & be scraped off to a sludge

collecting hopper.

Secondary treatment –In secondary process, dissolved oil & other organic

pollutants may be consumed biologically by microorganism..These processes

biologically degrade & oxidized soluble organic matter by the use of activated

sludge, unaerated or aerated lagoons, trickling filter methods. Materials with

high adsorption are used in fixed bed filters or added to the wastewater to form

slurry which is removed by sedimentation or filtration.

Tertiary treatment-It removes specific pollutants to meet regulatory discharge

requirements. These treatment includes chlorination, ozonations, ion exchange,

reverse osmosis, activated carbon adsorption etc.

Pre treatment (dewatering)-Dewatering means removing water from oil. This is

simple process relying on the separation of aq. & oil phases over time under the

influence of gravity.It involves following steps-a. Filtering & demineralization

b. Propane Deasphalting process & Distillation.

4 4

4-f Importance of vacuum distillation in refining operation:

The main objective of vacuum distillation is to maximize the recovery of

valuable distillate & to reduce the energy consumption of the units. Heavier

fractions from atmospheric distillation unit that cannot be distilled without

cracking under its pressure & temperature conditions are vacuum distilled.

4 4


5-a Esterification process in refineries. 4




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It is the reaction between alcohol and carboxylic acid to form ester.Unsaturated

vinyl ester for use in polymerization reactions are made by the esterification of

olefins. Vinyl acetate is made by reacting ethylene with acetic acid in the

vapour phase over a supported palladium catalyst.

CH2=CH2 + CH3COOH + 1/2 O2 →CH3COOCH=CH2 +H2O

Reaction takes place in a fixed bed tubular reactor at 175-2000c and 400-

1000KPa and is highly exothermic. Effluent from the reactor is sent to a phase

separator and the phases are separated. In the absorber the gas is washed with

acetic acid to recover the vinyl acetate.

4

5-b Reforming

Description: Catalytic reforming is used to convert hydrocarbonsto aromatics

which have high octane rating.

Naphtha feed is prepared in a fractionator. It is pretreated by mild

hydrogenation to remove the impurities which will poison the platinum catalyst

2

4




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and then mixed with recycle stream, preheated and charged to 3 or more

cylindrical fixed bed catalytic reactors in series. Reheat interstages are required

since the overall reaction is endothermic.

Flowsheet

2

5-c Manufacturing of styrene:

Description

Benzene is alkylated with ethylene using aluminum chloride or acid type

catalyst. The resulting ethyl benzene is catalytically dehydrogenated in steam or

excess benzene atmosphere to give styrene.

All benzene feed must be dried by azeotropic distillation. Ethyl chloride is

added to ethylene which is fed continuously with benzene to the alkylation

tower operated at 950c & 1 atm.Crude acidic ethyl benzene from the cooler is

neutralised with 50% NaOH,striped to remove polyethyl benzene & the

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overhead sent to benzene column which separates wet benzene from ethyl

benzene. Dehydrogenation of ethyl benzene is the step which produces styrene

The mixed feed passes through the preheated to achieve an input temp. Of

5000c.The dehydrogenation catalyst is promoted

Zinc,chromium,iron.Reactionproduct is cooled in the feed preheater ,then by

steam quenching. Hydrocarbon mixture is passed into a series of vacuum

distillation column to allow the separation of impurities at low temp to avoid

polymerization of styrene. The second column at 35mm & 900c reboiler temp

separate styrene from ethyl benzene.

Flowsheet




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2




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5-d Coking Process:

Initially the heavy feedstock (residue from atmospheric distillation unit) is fed

to a furnace which heats it to high temperature (480-510oc) at low pressures

(25-30 psi) and is designed & controlled to prevent premature coking in the

heater tubes. The hot mixture is passed from the heater to one or more coker

drums where it is held for approximately 24 hours until it cracks into lighter

products. Vapours from the drums are returned to fractionators, where gas,

naphtha etc are separated out. After the coke reaches predetermined level in one

drum, the flow is diverted to another drum to maintain continuous operation.

Full drum is steam stripped to remove to remove uncracked hydrocarbons,

cooled by water injection and decoked by mechanical or hydraulic methods.

( Any other type of coking should be given due consideration)

4

4

5-e Thermal cracking process:

Thermal cracking is a refining process in which heat ( 800oc ) and pressure

( 700KPa) are used to break down, rearrange hydrocarbon molecules.

Visbreaking, steam cracking, coking are applications of thermal cracking.

Visbreaking:

It is a mild form of thermal cracking which cracks large hydrocarbon molecules

4

4




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in the oil by heating in a furnace to reduce its viscosity and to produce small

quantities of light hydrocarbons. Residue from the atmospheric distillation

tower is heated in a heat exchanger to 250oC and then heated to 425-5100c at

atmospheric pressure and mildly cracked in a heater. It is then quenched with

cool gas oil to control over cracking and flashed in a distillation tower. The

thermally cracked residue tar which accumulates at the bottom of the tower is

vacuum flashed in a stripper and the distillate recycled.

Due weightage should be given forsteam cracking, delayed coking,

continuous coking etc)

5-f Constituents of crude oil:

Crude oil is made up of the following elements

1. carbon-84% 2. hydrogen -14%

3. sulphur-1-3% 4. nitrogen, oxygen, metals, salts- <1%

The major compounds present in crude oil are:

A. hydrcarbon

i)Paraffins

ii)Aromatics

iii) Napthenes

iv) dienes

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B. Non hydrocarbon

i) S compounds

ii)O2 compounds

iii)N2 compounds

C. Metallic compounds.

Four unit operation involved in refining process:

Distillation, extraction, absorption ,adsorption.

1/2 mark

each


6-a Difference between petroleum refinery and petrochemical industry.

Petroleum refinery Petrochemical industry

1)Process crude oil into different fractions.

It is a chemical plant that uses a petroleum based feedstock from petroleum refinery to produce a petrochemical product

2)Feed stock is crude oil from mines Feed stock is product obtained from Petroleum refinery

3)Product obtained from Refinery are kerosene, gasoline, diesel, LPG etc

Product obtained from petrochemical industry are plastic, different hydrocarbons

4) All refineries have more or less similar unit operations and unit processes

The process depends on the product to be produced.

1 mark

each

4

6-b Types of refineries.

1.Primary refinery

2. Intermediate refinery

3. Complex refinery

4 4

6-c Isomerization: Isomerization is used to convert n-paraffins to isoparaffins.

Description: Feed stock is dried preheated and fed to a reactor where efficient

contact between reactants and catalysts takes place. Catalyst is HCl promoted

1

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aluminiumtrichloride and reaction temperature is 100-1500c and pressure 17 to

27 atm. Removal of light ends by flashing , followed by HCl stripping, caustic

washing and fractionation are the standard operations performed to produce

isomerized gasoline.

Flowsheet

1.5

1.5

6-d Oetane number: Octane number is defined as the percentage volume of

isooctane in a mixture of isooctane and – heptanes that gives the same knocking

characteristics as the fuel under consideration

Cetane number:

It is defined as the percentage volume of n-cetane in a mixture of n-cetane and

heptamethylnonane that gives the same ignition delay as the fuel under

consideration.

2

2

4

6-e Flow sheet for the manufacture of ethanol:

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4

6-f Flow sheet for the manufacture of propylene oxide.

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